Abstract: Due to deep buried silty fine sand and sand gravel layers of strong permeability in the foundation of Xinglong hydropower project, the stability and seepage problem of the dam foundation are of great concern. By means of 3-D seepage analysis for the foundation of powerhouse segment and sluice segment, we compared the effects of different seepage control measures. Results reveal that under design water level condition, the exit gradient of foundation’s fine sand can be controlled less than 0.30 by taking some seepage control measures. When the downstream water level descents, the exit gradient of foundation fine sand will be larger than 0.30 behind the tail channel of powerhouse, and between 0.20 and 0.30 behind the sluice dam. The seepage stability of foundation fine sand is more relied on filter protection.

Key words: Xinglong hydropower project, seepage control, 3-D seepage analysis, coefficient of permeability, exit gradient